The objective of this research proposal is to study the relative role of lymphocytes from regional and distant lymph nodes, spleen, and peripheral blood by means of in vitro cell-mediated reactivity to syngeneic rat oral tumors. A microcytotoxicity assay is being used to determine levels of in vitro cytotoxicity at various stages of tumor progression. Oral tumors indiced by the chemical carcinogen dimethylbenzanthracene are being studied both in the primary host and in a transplantable tumor system. This study may provide a valuable model for the study of neoplasma of the oral cavity which may better clarify the roles of lymphocytes from various anatomical locations in the host defense mechanism against oral cancer.